This grant supports a program of research including the following research projects: 1. Prospective study of the relationship of endocrine factors and other selected components of the serum to the development of cancers of different sites. 2. Study of mortality and morbidity experience among workers in an arsenic plant. 3. Study of mortality and morbidity experience among workers in a chromate plant. 4. Epidemiological study of prostate cancer. 5. A retrospective study of brain tumours. 6. An epidemiological study of mortality emphasizing cancer of the cervix in the Amish and non-Amish populations of selected counties in Indiana and Ohio. 7. Study of breast cancer incidence among women with a history of infertility.